Under circumstances where 2G and 3G networks coexist for a long time, interworking between 2G and 3G frequently occurs. Through the convergence on the access network device side, an Iur-g interface between a base station controller (Base Station controller, BSC) and a radio network controller (Radio Network Controller, RNC) is used to optimize the handover procedure, so that the Iur-g interface bears a signaling plane and a user plane at the same time. In this way, the inter-system handover success rate may be improved.
After an air interface is handed over from 3G to 2G, the RNC may migrate the user plane from the Iur-g interface to the A interface at a proper time, and release Iur-g interface resources. In this way, the user is migrated to 2G completely, and successive handovers are avoided.
Referring to FIG. 1, currently an optional procedure for migrating a user plane from an Iur-g interface to an A interface is as follows:
(1) When a RNC judges that it is required to perform migration from the Iur-g interface to the A interface, a relocation required (Relocation Required) message is sent to a core network.
(2) After the BSC receives a handover request (Handover Request) message sent by the core network, finishes preparing A interface resources, deploys a network at a user plane of the A interface, and removes a user plane of the Iur-g interface, it sends a handover request acknowledge (Handover Request Acknowledge) message, a handover detect (Handover Detect) message, and a handover complete (Handover Complete) message to the core network successively.
(3) After the core network receives the Handover Complete message sent by the BSC, an Iu interface release command (Iu Release Command) message is sent to the RNC, triggering the RNC to release Iur-g interface resources.
The inventor finds that, in the foregoing handover procedure: After the BSC receives a handover request message from the core network, the BSC actively implements a whole process of handing over the user plane from the Iur-g interface to the A interface, which causes a long interruption of the user plane during the handover.